Rotary compressor

ABSTRACT

A rotary compressor for preventing, to the maximum extent possible, oil within the compressor from being discharged to a gas discharge port. The rotary compressor includes a drive device and a compression device which are mounted in a hermetic container. The hermetic container includes an upper cover formed with a gas discharge port. The rotary compressor includes a scroll chamber defined in an inner surface of the upper cover around the discharge port, to separate oil from gas to be discharged, and a discharge guiding member installed inside the upper cover, to guide the gas, discharged from the hermetic container, into the scroll chamber and to guide the gas, having passed through the scroll chamber, to the discharge port.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Applications No. 2006-0107236 and No. 2006-107235, filed on Nov. 1, 2006 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotary compressor, and, more particularly, to a rotary compressor capable of preventing, to the maximum extent possible, oil within the compressor from being discharged toward a refrigerant gas discharge port.

2. Description of the Related Art

Korean Patent Laid-open Publication No 10-2004-0023069 (published on Mar. 18, 2004) discloses a rotary compressor in which an oil flow path is formed in a rotating shaft, to supply oil gathered in a bottom region of a hermetic container to a compression device during operation of the compressor.

The oil flow path includes an upright flow path perforated from a lower end to an upper end of the rotating shaft, and a radial communication flow path to communicate the upright flow path with an outer surface of the rotating shaft. When the rotating shaft is rotated at a high speed, accordingly, oil is ejected radially through the communication flow path and supplied to the compression device, thereby acting to lubricate or cool frictional portions of the compression device.

However, the above described rotary compressor has a problem in that the amount of oil gathered in the compressor may be gradually reduced as time passes. This is because particulate-phase oil, as a part of the oil radially ejected through the communication flow path, is mixed with refrigerant gas within the hermetic container to thereby be discharged toward a refrigerant gas discharge port.

If the amount of oil within the compressor is reduced, it is difficult to achieve efficient lubrication and cooling of the compression device and drive device of the compressor and consequently, the compressor may suffer from many problems, for example, overheating, malfunction, and performance degradation. Furthermore, the oil discharged through the discharge port along with the refrigerant gas may have a risk of forming an oil film at an inner surface of a heat exchanger or pipe included in a cooling system employing the compressor. This results in a degradation in the efficiency of heat exchange and consequently, a degradation in the performance of the cooling system.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve the above problems. It is an aspect of the invention to provide a rotary compressor capable of preventing, to the maximum extent possible, oil within the compressor from being discharged toward a refrigerant gas discharge port.

Consistent with one aspect, an exemplary embodiment of the present invention provides a rotary compressor including a hermetic container, and a drive device and a compression device mounted in the hermetic container, the hermetic container having an upper cover formed with a gas discharge port, the rotary compressor further including: a scroll chamber defined in an inner surface of the upper cover around the discharge port, to separate oil from gas to be discharged; and a discharge guiding member installed inside the upper cover, to guide the gas, discharged from the hermetic container, into the scroll chamber and to guide the gas, having passed through the scroll chamber, to the discharge port.

The scroll chamber may be opened downwardly and include an inner curved surface upwardly recessed from the inner surface of the upper cover, the scroll chamber being circularly disposed around the discharge port.

The discharge guiding member may include: a circular plate portion installed below the discharge port so as to be spaced apart from the inner surface of the upper cover, an outer diameter of the circular plate portion being determined such that a rim of the circular plate portion is located close to the scroll chamber; and a protrusion portion protruding from an upper surface of the circular plate portion toward the discharge port, to guide discharge of the gas.

The rotary compressor may further include: a discharge flow path provided between the upper cover and the discharge guiding member to guide the gas from the scroll chamber to the discharge port, the discharge flow path having an U-shaped oil trap for separation of the oil from the gas; and an oil discharge hole formed in the discharge guiding member to discharge the oil gathered in a bottom region of the U-shaped oil trap.

The upper cover may include a bell-mouse shaped inner surface forming a top surface of the discharge flow path, and the protrusion portion may include a conical outer surface spaced apart from the bell-mouse shaped inner surface, the conical outer surface forming a bottom surface of the discharge flow path.

The conical outer surface of the protrusion portion and the upper surface of the circular plate portion may form a continuous curved surface together.

The upper surface of the circular plate portion may include an U-shaped curved surface forming a bottom surface of the U-shaped oil trap, the U-shaped curved surface and the conical outer surface of the protrusion portion forming a continuous curved surface together.

The rotary compressor may further include: a first raised oil-shield portion taking the form of a stepped portion provided at a boundary between the bell-mouse shaped inner surface of the upper cover and the scroll chamber and a second raised oil-shield portion taking the form of a convex curved portion provided on the rim of the circular plate portion, for separating the oil from the gas being introduced into the discharge flow path.

The discharge port may be provided at the center of the upper cover, and centers of the discharge port, the scroll chamber, and the discharge guiding member coincide with one another.

At least one whirling blade may be formed at an outer surface of the protrusion portion, to whirl the gas flowing to the discharge port.

An inclined guiding surface may be provided at the rim of the circular plate portion, to guide the rising gas from the interior of the hermetic container into the scroll chamber.

The rotary compressor may further include: a spacer member interposed between the discharge guiding member and the inner surface of the upper cover; and a fastening member to secure the discharge guiding member to the upper cover.

The drive device may include a stator secured to an inner surface of the hermetic container and a rotor rotatably installed inside the stator, and the oil discharge hole may be inclined toward the center of the rotor.

Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the exemplary embodiments of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:

FIG. 1 is a sectional view showing the configuration of a rotary compressor consistent with the present invention;

FIG. 2 is a sectional view showing an oil collecting device of the rotary compressor consistent with a first embodiment of the present invention;

FIG. 3 is a perspective view showing a discharge guiding member of the rotary compressor consistent with the first embodiment of the present invention;

FIG. 4 is a sectional view showing an oil collecting device of the rotary compressor consistent with a second embodiment of the present invention;

FIG. 5 is a perspective view showing a discharge guiding member of the rotary compressor consistent with the second embodiment of the present invention; and

FIG. 6 is a sectional view showing an oil collecting device consistent with a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.

The rotary compressor consistent with the present invention, as shown in FIG. 1, includes a hermetic container 10, a drive device 20 installed in an upper region of the hermetic container 10 and adapted to generate a rotating force, and a compression device 30 installed in a lower region of the hermetic container 10 and connected to the drive device 20 through a rotating shaft 21.

The hermetic container 10 includes a cylindrical body 11, a lower cover 12 coupled to a lower end of the body 11, and an upper cover 13 coupled to an upper end of the body 11. Both the lower cover 12 and the upper cover 13 are coupled to the body 11 by welding, etc., so as to seal the upper and lower ends of the body 11.

The drive device 20 includes a cylindrical stator 22 secured to an inner surface of the body 11 of the hermetic container 10, and a rotor 23 rotatably installed inside the stator 22 and centrally coupled to the rotating shaft 21.

The compression device 30 includes a cylinder body 32 centrally defining a cylindrical compression chamber 31 therein, and upper and lower flanges 33 and 34 coupled to upper and lower surfaces of the cylinder body 32 to cover upper and lower ends of the cylinder body 32. The upper flange 33 has a cylindrical upper shaft supporting portion 35, which extends upward from the flange 33 by a predetermined length to support the rotating shaft 21. The lower flange 34 has a cylindrical lower shaft supporting portion 36, which extends downward from the flange 34 by a predetermined length to support the rotating shaft 21. All the upper flange 33, cylinder body 32, and lower flange 34 are firmly coupled with one another by means of a plurality of fastening bolts 37. The cylinder body 32 has an outer diameter corresponding to an inner diameter of the hermetic container 10 such that the cylinder body 32 is secured close to the inner surface of the hermetic container 10. The rotating shaft 21 is penetrated through the center of the compression chamber 31 and rotatably supported by both the upper shaft supporting portion 35 and the lower shaft supporting portion 36.

The compression device 30 further includes an eccentric portion 38 located in the compression chamber 31 around the rotating shaft 21, and a ring piston 39 rotatably installed to an outer surface of the eccentric portion 38, the ring piston 39 having an outer surface coming into contact with an inner surface of the compression chamber 31. Although not shown in the drawings, the compression device 30 further includes a vain that is reciprocally movable in a radial direction by rotation of the ring piston 39 so as to divide the interior of the compression chamber 31 into a suction part and a discharge part, and a vain spring to press the vane toward the ring piston 39.

The cylinder body 32 has a suction port 41 that communicates with the suction part of the compression chamber 31 to allow refrigerant gas to be introduced into the compression chamber 31. The upper flange 33 has a discharge port 42 for discharge of the compressed refrigerant gas. The suction port 41 is connected to a refrigerant suction pipe 43 such that low-pressure refrigerant delivered from an evaporator of a general cooling system is introduced into the suction port 41. The upper cover 13 of the hermetic container 10 has a discharge port 44 formed at the center thereof for discharging the compressed refrigerant gas out of the hermetic container 10. The discharge port 44 is connected to a discharge pipe 45. In FIG. 1, reference numeral 46 denotes an accumulator coupled to the refrigerant suction pipe 43.

The rotating shaft 21 has a first oil flow path 51 and a second oil flow path 52 formed therein, to supply oil filled in a bottom region of the hermetic container 10 to frictional portions of the compression device 30. The first oil flow path 51 is perforated through the rotating shaft 21 from a lower end to an upper end of the rotating shaft 21, and the second oil flow path 52 is formed in a radial direction of the rotating shaft 21 to communicate the first oil flow path 51 with the outside of the rotating shaft 21. If necessary, a plurality of second oil flow paths 52 may be provided at different positions including an upper position or an intermediate position of the upper shaft supporting portion 35. With this configuration, if oil rises along the first oil flow path 51 by a centrifugal force generated during rotation of the rotating shaft 21, the oil is scattered out of the rotating shaft 21 through the second oil flow path 52, so as to be supplied to frictional potions of the compression device 30. To facilitate the rising of the oil through the first oil flow path 51, an oil pickup member 53 having a spiral blade shape may be installed at a lower end of the first oil flow path 51.

In the above described rotary compressor, if the rotating shaft 21 is rotated by operation of the drive device 20, the eccentric portion 38 within the compression chamber 31 is rotated, and simultaneously the ring piston 39 is eccentrically rotated in the compression chamber 31 by operation of the eccentric portion 38. With the eccentric rotation of the ring piston 39, the suction part and the discharge part of the compression chamber 31 have a variation in volume. As a result, refrigerant gas is suctioned into the compression chamber 31 through the suction port 41. After being compressed in the compression chamber 31, the refrigerant gas is discharged to the interior of the hermetic container 10 through the discharge port 42. The compressed refrigerant gas within the hermetic container 10 flows upward through a gap 25 between the stator 22 and the rotor 23, to thereby be discharged into the discharge pipe 45 through the discharge port 44 of the upper cover 13. During the above described operation of the compression device 30, oil is supplied to frictional portions of the compression device 30 through the first and second oil flow paths 51 and 52, so as to achieve lubrication and cooling of the compression device 30.

Meanwhile, during the above described compressing operation, particulate-phase oil scattered from the second oil flow path 52 may flow toward the discharge port 44 of the upper cover 13 along with the compressed refrigerant gas. In the present invention, an oil collecting device 60 is provided in the upper cover 13 to collect the scattered oil, so as to prevent the discharge of oil to the maximum extent possible. Hereinafter, the oil collecting device 60 will be described.

FIGS. 2 and 3 illustrate the oil collecting device 60 consistent with a first embodiment of the present invention. The oil collecting device 60 of the first embodiment, as shown in FIG. 2, includes a scroll chamber 61 defined in an inner surface of the upper cover 13, and a discharge guiding member 70 installed near the inner surface of the upper cover 13 to define a discharge flow path 62 along with the inner surface of the upper cover 13, the discharge guiding member 70 allowing the refrigerant gas within the hermetic container 10 to be discharged to the discharge port 44 by way of the scroll chamber 61. The discharge flow path 62 has an U-shaped oil trap 66 for collecting the oil in the course of discharging the refrigerant gas. The discharge guiding member 70 has a plurality of oil discharge holes 77 for discharging the oil gathered in the U-shaped oil trap 66.

The scroll chamber 61 is defined in the inner surface of the upper cover 13 at a position close to a side surface of the upper cover 13, to have a circular shape encircling the discharge port 44. The scroll chamber 61 has an inner curved surface 63 that is upwardly recessed from the inner surface of the upper cover 13. The scroll chamber 61 is opened downwardly for allowing the rising refrigerant gas to be introduced into the scroll chamber 61. The inner curved surface 63 of the scroll chamber 61 has a semi-circular or oval cross section.

The upper cover 13 has a bell-mouse shaped inner surface 64, which is connected to the discharge port 44 so as to guide the refrigerant gas, having passed through the scroll chamber 61, to the discharge port 44, the bell-mouse shaped inner surface 64 forming a top surface of the discharge flow path 62. The discharge guiding member 70 is spaced apart downward from the bell-mouse shaped inner surface 64, to define the discharge flow path 62 along with the bell-mouse shaped inner surface 64. That is to say, the discharge guiding member 70 forms a bottom surface of the discharge flow path 62.

The discharge guiding member 70, as shown in FIGS. 2 and 3, includes a circular plate portion 71 spaced apart from the inner surface of the upper cover 13, an outer diameter of the circular plate portion 71 being determined such that a rim of the circular plate portion 71 is located adjacent to the scroll chamber 61, and a protrusion portion 72 protruding from the center of an upper surface of the circular plate portion 71 toward the discharge port 44. The protrusion portion 72 has a conical outer surface 73 spaced apart from the bell-mouse shaped inner surface 64 of the upper cover 13. The upper surface of the circular plate portion 71 has an U-shaped curved surface 74 forming a bottom surface of the U-shaped oil trap 66. The U-shaped curved surface 74 and the conical outer surface 73 of the protrusion portion 72 form a continuous curved surface. The oil discharge holes 77 are perforated from the deepest position of the U-shaped curved surface 74 to a lower surface 75 of the circular plate portion 71. This is to allow the oil gathered in the U-shaped oil trap 66 to fall down through the oil discharge holes 77. In this case, it is desirable that the oil discharge holes 77 be located as close as possible to the center of the rotor 23, or be inclined toward the center of the rotor 23 for the sake of efficient falling of the oil. This is to prevent the oil falling from the oil discharge holes 77 to avoid a stream of the refrigerant gas rising through the gap 25 between the stator 22 and the rotor 23, thereby preventing, to the maximum extent possible, the falling oil from being introduced again into the scroll chamber 61 by the rising stream of the refrigerant gas.

With the above described configuration, the upper surface of the discharge guiding member 70 and the bell-mouse shaped inner surface 64 of the upper cover 13 define the curved discharge flow path 62 having a low flow resistance, thereby allowing the refrigerant gas to be efficiently discharged from the scroll chamber 61 toward the discharge port 44. To ensure efficient discharge of the refrigerant gas, it is desirable that centers of the discharge port 44, scroll chamber 61, and discharge guiding member 70 coincide with one another, to allow a length of the discharge flow path 62 from the scroll chamber 61 to the discharge hole 44 to be constant in all directions.

As shown in FIG. 2, the circular plate portion 71 of the discharge guiding member 70 has an inclined guiding surface 76 formed at the lower side of the rim thereof. The inclined guiding surface 76 serves to guide the rising refrigerant gas from the interior of the hermetic container 10 into a corner of the scroll chamber 61. Accordingly, after the rising refrigerant gas collides against the inner surface of the scroll chamber 61, the refrigerant gas temporarily stays in the scroll chamber 61 so as to be whirled in the scroll chamber 61. This is to allow the oil, which is rising along with the refrigerant gas, to be adhered to the inner curved surface 63 of the scroll chamber 61, so as to be separated from the refrigerant gas.

To facilitate separation of the oil from the refrigerant gas being introduced into the discharge flow path 62 through the scroll chamber 61, a first raised oil-shield portion 65 and a second raised oil-shield portion 78 are formed at an entrance side of the discharge flow path 62. The first oil-shield portion 65 is a stepped portion formed at a boundary between the bell-mouse shaped inner surface 64 of the upper cover 13 and the scroll chamber 61. The second oil-shield portion 78 is a convex curved portion formed at the upper side of the rim of the circular plate portion 71. As the oil contained in the refrigerant gas flows from the scroll chamber 61 into the discharge flow path 62, the oil is able to be separated from the refrigerant gas by colliding against the first and second raised oil-shield portions 65 and 78. Accordingly, the first and second raised oil-shield portions 65 and 78 have the effect of improving the separation efficiency of the oil.

As shown in FIGS. 1 and 3, a plurality of spacer members 81 are provided at the upper surface of the discharge guiding member 70, to space the discharge guiding member 70 apart from the inner surface of the upper cover 13. A plurality of fastening screws 82 for securing the discharge guiding member 70 to the upper cover 13 are fastened into the spacer members 81. Although the spacer members 81 are integrally formed with the discharge guiding member 70 as illustrated in FIG. 3, the spacer members 81 may be formed as separate elements. Further, although the fastening bolts 82 are fastened into the spacer members 81 by penetrating through the upper cover 13 as illustrated in FIG. 1, the present invention is not limited thereto, and the fastening bolts 82 may be fastened by penetrating through the discharge guiding member 70. Alternatively, the discharge guiding member 70 may be secured to the upper cover 13 by other fastening means, for example, protruded portions of the discharge guiding member 70, rather than the fastening bolts.

Now, an oil collecting operation performed by the above described oil collecting device 60 will be described.

As shown in FIG. 2, the rising refrigerant gas from the interior of the hermetic container 10 collides against the lower surface 75 of the discharge guiding member 70 and thus, further rising of the refrigerant gas is not allowed. Therefore, the refrigerant gas is guided toward the scroll chamber 61, and more particularly, guided to the corner of the scroll chamber 61 by the inclined guiding surface 76 provided at the rim of the discharge guiding member 70. Accordingly, the oil, which rises along with the refrigerant gas, collides against the lower surface 75 and the inclined guiding surface 76 of the discharge guiding member 70, to thereby be adhered thereto. This causes an increase in the size of oil droplets, thus causing the oil to fall down. Also, once the oil is introduced into the scroll chamber 61 along with the refrigerant gas, the oil collides against the inner curved surface 63 of the scroll chamber 61 to thereby be adhered to the inner curved surface 63 and consequently, the oil falls down along the inner surface of the scroll chamber 61.

The refrigerant gas, having passed through the scroll chamber 61, flows toward the discharge port 44 through the discharge flow path 62. Similarly, a part of the oil contained in the refrigerant gas collides against the first and second raised oil-shield portions 65 and 78 provided at the entrance side of the discharge flow path 62, thereby being separated from the refrigerant gas. Furthermore, in the course that the refrigerant gas passes through the U-shaped oil trap 66 of the discharge flow path 62, the oil is adhered to the inner surface of the U-shaped oil trap 66 to thereby be separated from the refrigerant gas. In this case, the oil gathered in the bottom region of the U-shaped oil trap 66 falls down through the oil discharge holes 77.

As stated above, in the present invention, the oil is primarily separated from the refrigerant gas by the lower surface 75 and the inclined guiding surface 76 of the discharge guiding member 70, secondarily separated in the scroll chamber 61, and thirdly separated by the first and second raised oil-shield portions 65 and 78. In addition, the oil is fourthly separated by the U-shaped oil trap 66 of the discharge flow path 62. Consequently, the discharge of oil through the discharge port 44 can be prevented to the maximum extent possible.

The discharge flow path 62 is tapered such that a cross section of the discharge flow path 62 gradually decreases from the scroll chamber 61 to the discharge port 44. Accordingly, the pressure of the refrigerant gas increases in the course of being discharged through the discharge flow path 62. That is to say, the refrigerant gas to be discharged is gathered from the surrounding scroll chamber 61 to the discharge port 44 through the discharge flow path 62 and thus, subjected to an increase in pressure in the course of being discharged.

FIGS. 4 and 5 illustrate an oil collecting device consistent with a second embodiment of the present invention. As compared to that of the above described first embodiment, the oil collecting device 160 of the second embodiment further includes a plurality of whirling blades 183, which are installed at an outer surface of a protrusion portion 172 of a discharge guiding member 170 to cause the discharge gas to be whirled. Other configurations of the present embodiment are identical to those of the first embodiment. For example, a scroll chamber 161, first and second raised oil-shield portions 165 and 178, circular plate portion 171 of the discharge guiding member 170, inclined guiding surface 176 of the circular plate portion 171, U-shaped oil trap 166, oil discharge holes 177, spacer members 181, and the like are identical to those of the first embodiment.

The plurality of whirling blades 183 are spirally bent in a rotating direction of the rotor 23 of the drive device 20. With this configuration, the whirling blades 183 produce a whirling stream of the refrigerant gas having the same direction as the rotating direction of the rotor 23 and this has the effect of facilitating the flow of the refrigerant gas to be discharged to the discharge port 44. Specifically, since the rising refrigerant gas from the interior of the hermetic container 10 is introduced into the scroll chamber 161 while being whirled in a predetermined direction by a rotating movement of the rotor 23, the refrigerant gas has a tendency of being whirled in the predetermined direction when being discharged from the scroll chamber 161 into a discharge flow path 162. Accordingly, by guiding the discharge refrigerant gas to be whirled in the predetermined direction (i.e. in the rotating direction of the rotor 23) by the whirling blades 183, it is possible to achieve efficient flow of the refrigerant gas to be discharged.

FIG. 6 illustrates an oil collecting device consistent with a third embodiment of the present invention. As compared to the above described first embodiment, the oil collecting device of the third embodiment has no U-shaped oil trap and oil discharge holes. In this case, the circular plate portion 71 has a flat upper surface. Other configurations of the present embodiment are identical to those of the first embodiment.

As apparent from the above description, the present invention provides a rotary compressor having the following effects.

Firstly, according to the present invention, oil contained in refrigerant gas to be discharged is primarily separated by a lower surface and an inclined guiding surface of a discharge guiding member, secondarily separated by an inner surface of a scroll chamber, and thirdly separated in the course of passing through a discharge flow path. This has the effect of preventing the discharge of oil through a refrigerant gas discharge port to the maximum extent possible.

Secondly, in the course of being discharged through the discharge flow path, the oil is separated by first and second raised oil-shield portions and additionally, separated by an U-shaped trap of the discharge flow path, so as not to be discharged out of the compressor to the maximum extent possible.

Thirdly, the present invention has the function of collecting the oil, gathered in the discharge flow path, by use of oil discharge holes, and therefore, has the effect of achieving a further reduction in potential discharge of oil.

Finally, according to the present invention, refrigerant gas to be discharged is guided to be whirled in the same direction as a rotating direction of a rotor by whirling blades. This has the effect of ensuring more efficient flow of the refrigerant gas to be discharged.

Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. 

1. A rotary compressor comprising a hermetic container, and a drive device and a compression device mounted in the hermetic container, the hermetic container having an upper cover formed with a gas discharge port, the rotary compressor further comprising: a scroll chamber defined in an inner surface of the upper cover around the discharge port, to separate oil from gas to be discharged; and a discharge guiding member installed inside the upper cover, to guide the gas, discharged from the hermetic container, into the scroll chamber and to guide the gas, having passed through the scroll chamber, to the discharge port.
 2. The rotary compressor according to claim 1, wherein the scroll chamber is opened downwardly and comprises an inner curved surface upwardly recessed from the inner surface of the upper cover, the scroll chamber being circularly disposed around the discharge port.
 3. The rotary compressor according to claim 2, wherein the discharge guiding member comprises: a circular plate portion installed below the discharge port so as to be spaced apart from the inner surface of the upper cover, an outer diameter of the circular plate portion being determined such that a rim of the circular plate portion is located close to the scroll chamber; and a protrusion portion protruding from an upper surface of the circular plate portion toward the discharge port, to guide discharge of the gas.
 4. The rotary compressor according to claim 3, further comprising: a discharge flow path provided between the upper cover and the discharge guiding member to guide the gas from the scroll chamber to the discharge port, the discharge flow path having an U-shaped oil trap for separation of the oil from the gas; and an oil discharge hole formed in the discharge guiding member to discharge the oil gathered in a bottom region of the U-shaped oil trap.
 5. The rotary compressor according to claim 4, wherein the upper cover comprises a bell-mouse shaped inner surface forming a top surface of the discharge flow path, and the protrusion portion comprises a conical outer surface spaced apart from the bell-mouse shaped inner surface, the conical outer surface forming a bottom surface of the discharge flow path.
 6. The rotary compressor according to claim 5, wherein the conical outer surface of the protrusion portion and the upper surface of the circular plate portion form a continuous curved surface together.
 7. The rotary compressor according to claim 5, wherein the upper surface of the circular plate portion comprises an U-shaped curved surface forming a bottom surface of the U-shaped oil trap, the U-shaped curved surface and the conical outer surface of the protrusion portion forming a continuous curved surface together.
 8. The rotary compressor according to claim 5, further comprising: a first raised oil-shield portion taking the form of a stepped portion provided at a boundary between the bell-mouse shaped inner surface of the upper cover and the scroll chamber and a second raised oil-shield portion taking the form of a convex curved portion provided on the rim of the circular plate portion, for separating the oil from the gas being introduced into the discharge flow path.
 9. The rotary compressor according to claim 8, wherein the discharge port is provided at the center of the upper cover, and centers of the discharge port, the scroll chamber, and the discharge guiding member coincide with one another.
 10. The rotary compressor according to claim 3, wherein at least one whirling blade is formed at an outer surface of the protrusion portion, to whirl the gas flowing to the discharge port.
 11. The rotary compressor according to claim 3, wherein an inclined guiding surface is provided at the rim of the circular plate portion, to guide the rising gas from the interior of the hermetic container into the scroll chamber.
 12. The rotary compressor according to claim 3, further comprising: a spacer member interposed between the discharge guiding member and the inner surface of the upper cover; and a fastening member to secure the discharge guiding member to the upper cover.
 13. The rotary compressor according to claim 4, wherein the drive device comprises a stator secured to an inner surface of the hermetic container and a rotor rotatably installed inside the stator, and the oil discharge hole is inclined toward the center of the rotor.
 14. A rotary compressor, comprising: a hermetic container having an upper cover formed with a gas discharge port; a drive device and a compression device mounted in the hermetic container; an oil collecting device to separate oil from gas to be discharged, wherein the oil collecting device comprises: a scroll chamber formed as an inner curved surface upwardly recessed from the inner surface of the upper cover and circularly disposed around the gas discharge port, a discharge guiding member to guide the gas discharged from the hermetic container into the scroll chamber.
 15. The rotary compressor according to claim 14, wherein the discharge guiding member comprises: a circular plate portion installed below the discharge port and spaced apart from the inner surface of the upper cover; and a protrusion portion protruding from an upper surface of the circular plate portion toward the discharge port, to guide discharge of the gas.
 16. The rotary compressor according to claim 15, further comprising: a U-shaped oil trap for separation of the oil positioned between the upper cover and the discharge guiding member; and an oil discharge hole formed in the discharge guiding member to discharge the oil gathered in a bottom region of the U-shaped oil trap.
 17. The rotary compressor according to claim 15, further comprising: a first raised oil-shield portion formed as a stepped portion in the inner surface of the upper cover; and a second raised oil-shield portion formed as a convex curved portion provided on the rim of the circular plate portion.
 18. The rotary compressor according to claim 15, further comprising at least one whirling blade formed at an outer surface of the protrusion portion. 